Kadin, U.S. Pat. No. 4,556,672 disclosed 2-oxindole-1-carboxamides of the formula ##STR1## and pharmaceutical salts thereof which include tenidap and its salts.
Allen and O'Neill, U.S. Pat. No. 5,036,099 disclosed an anhydrous crystalline form of the sodium salt of tenidap which is nonhygroscopic and stable in dosage forms.
Tenidap and other 2-oxindole-1-carboxamides are acute phase protein modulating anti-inflammatory drugs which are useful for the treatment of rheumatoid arthritis. Similar to the steroids, these compounds have been shown to cause rapid reduction in acute phase proteins in arthritic patients. Intra-articular administration of these compounds relieves joint pain and swelling while minimizing systemic drug exposure. Prolonged-acting formulations employing sparingly soluble salts are required for intra-articular administration.